On certain types of aircraft, the engines are fixed at the rear section of the fuselage rather than suspended beneath the wing structure as in the more conventional case. Alternatively, an engine may be fixed to the vertical empennage of the aircraft, again at the rear section thereof.
Engines are mounted using complex mounting devices, also referred to as “EMS” (which stands for “Engine Mounting Structure”), or even mounting struts. The mounting devices usually employed have a rigid structure referred to as primary structure. This primary structure forms a box section, i.e. is made up of an assembly of lower and upper spars joined together by a plurality of transverse stiffening ribs situated inside the box section.
The primary structure of these struts is designed to allow the static and dynamic forces generated by the engines, such as the weight, the thrust, or even the various dynamic forces to be transmitted to the fuselage or to the empennage.
The transmission of forces between the engine and the primary structure is performed conventionally by mounting comprising a front engine mount, one or more rear engine mounts, and a device that reacts thrust forces. The latter device usually comprises two lateral link rods for reacting the thrust forces, these being arranged symmetrically and connected to the rigid structure near the front engine mount. Alternatively, a mount referred to as a “spigot mount” may be provided, allowing thrust forces to be transmitted in shear.
Although this solution is satisfactory overall, there is still room for improvement in terms of engine deformation. Indeed, the engine deformation observed during operation, particularly deformation caused by flexing along the transverse axis of the engine, leads to blade tip rotor wear. This wear increases the clearances between the blades and the casings that surround them, resulting in a drop in the overall efficiency of the engine and in a reduction of the life thereof.